Young tools rewrite old history

Scientists have uncovered the youngest known Middle Stone Age tools in modern-day Senegal, on the west coast of Africa, dated to as recently as 11,000 years ago.

Their results are published in Scientific Reports and drive home the point that human culture hasn’t evolved in a neat, universal sequence.

These types of tools – sharp flakes produced by distinctive methods, some shaped into ‘scrapers’ and ‘points’ – most commonly occur in Africa between 300,000 and 30,000 years ago. Scientists have long thought that these were replaced by a radically different toolkit, smaller and better suited to the changing ways humans obtained food and moved through the landscape. 

“Prior to our work, the story from the rest of Africa suggested that well before 11,000 years ago, the last traces of the Middle Stone Age – and the lifeways it reflects – were long gone,” says lead author Khady Niang from the Cheikh Anta Diop University in Senegal.

This new research confirms that story is wrong.

According to Eleanor Scerri, the co-lead author from the Max Planck Institute for the Science of Human History in Germany, West Africa is a frontier for human evolutionary studies.

“We know almost nothing about what happened here in deep prehistory,” she says. “Almost everything we know about human origins is extrapolated from discoveries in small parts of eastern and southern Africa.”

It’s difficult to pinpoint exactly why humans in this area still used “old” technologies so recently, though the team stresses that it doesn’t correlate with a lack of capacity in these populations.

“These people were intelligent – they knew how to select good stone for their tool making and exploit the landscape they lived in,” says Niang.

Instead, the researchers suspect the late persistence of these technologies may be related to the region’s relative isolation, with the Sahara Desert in the north and the Central African rainforests to the east, which were often cut off from West African rainforests during droughts. Groups of hunter-gatherers scattered across these areas were therefore subjected to different climatic and environmental pressures.

“Apart from physical distance, it may be the case that some cultural boundaries also existed,” says Niang. “Perhaps the populations using these different material cultures also lived in slightly different ecological niches.”

“It is also possible that this region of Africa was less affected by the extremes of repeated cycles of climate change,” adds Scerri. “If this was the case, the relative isolation and habitat stability may simply have resulted in little need for radical changes in subsistence, as reflected in the successful use of these traditional toolkits.”

Around 15,000 years ago, central and Western Africa saw a major increase in humidity and forest growth. This may have prompted migration and thus genetic and cultural mixing – causing these Middle Stone Age tools to slowly vanish.

The research bolsters the emerging view that human culture didn’t evolve linearly, in a straightforward march towards modernity. Rather, the timing varied widely across populations.

“Groups of hunter-gatherers embedded in radically different technological traditions occupied neighbouring regions of Africa for thousands of years, and sometimes shared the same regions,” Scerri says.

“Long isolated regions, on the other hand, may have been important reservoirs of cultural and genetic diversity. This may have been a defining factor in the success of our species.”